644531901771 has 16 divisors (see below), whose sum is σ = 863245634048. Its totient is φ = 427755621600.

The previous prime is 644531901697. The next prime is 644531901781. The reversal of 644531901771 is 177109135446.

It is a de Polignac number, because none of the positive numbers 2^k-644531901771 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644531901771.

It is not an unprimeable number, because it can be changed into a prime (644531901781) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 685236 + ... + 1326126.

It is an arithmetic number, because the mean of its divisors is an integer number (53952852128).

Almost surely, 2^644531901771 is an apocalyptic number.

644531901771 is a deficient number, since it is larger than the sum of its proper divisors (218713732277).

644531901771 is a wasteful number, since it uses less digits than its factorization.

644531901771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642402.

The product of its (nonzero) digits is 635040, while the sum is 48.

The spelling of 644531901771 in words is "six hundred forty-four billion, five hundred thirty-one million, nine hundred one thousand, seven hundred seventy-one".